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<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>并集选择器</title>
  <style>
    h2,h3,p{color: red;font-size: 14px}
    h3,.special,#one{text-decoration: underline;}
  </style>
</head>
<body>
<h2>二级标题文本</h2>
<h3>三级标题文本</h3>
<p>段落文本1，普通文本</p>
<p class="special">段落文本2，加下划线</p>
<p id="one">段落文本3，加下划线</p>
</body>
</html>